1. Field of the Invention
The present invention relates to a novel silicon-urethane (meth)acrylate, as well as to a resin composition and a coating material for optical fiber comprising said silicon-urethane (meth)acrylate which is useful particularly as an ultraviolet-curable coating material to be applied to glass surface of optical fiber to protect it.
2. Description of the Prior Art
Since optical fiber has a high information-transmitting performance and it is relatively insusceptible to the external interference, its use has markedly increased in the later several years particularly in the field of communications. Optical fibers are generally made of glass, because they are used in the field of communications. However, glass fiber is fragile in its nature and can be chemically deteriorated by steam, so that it is readily breakable and difficult to handle. Accordingly, it has hitherto been conventional to coat glass fibers with a resin. As the resin for coating glass fibers, epoxy resin, urethane resin and the like have so far been used. However, these resins are disadvantageous in that they are inferior in productivity because their cure takes a long period of time and they are poor in flexibility so that transmitting performance of glass fiber can be deteriorated by lateral pressure. With the aim of overcoming the above-mentioned disadvantages, ultraviolet-curable compositions comprising urethane acrylate have energetically been studied recently, and ultraviolet-curable composition for optical glass fiber and a method for forming its coating film have been proposed in, for example, Japanese Patent Kokai (Laid-Open) No. 223,638/83 and EP 111,280.
Further, with the aim of improving the adhesion to glass, an ultraviolet-curable coating material for optical glass has been proposed in EP 149,741.
According to EP 149,741, polyalkoxysilane having one amino group or mercapto group is added to improve adhesion to glass. However, this composition has a problem that viscosity of the liquid can increase and gelation can take place, though the composition is excellent in adhesion to glass.